Fluorescent spectral analysis



April 14, 1953 FLUORESCENT Filed 001,. 24, 1949 M. A. CORDOVI 2,635,192

SPECTRAL ANALYSIS 5 Sheets-Sheet l 1%1-53 30 SLIDE SCAN (D F I 6. I

INVENTOR fl ggrcel A. Cordow ATTORNEY April 14, 1953 M. A. CORDOVIFLUORESCENT SPECTRAL ANALYSIS 5 Sheets-Sheet 2 Filed 001,. 24, 1949 96FIG. 2

INVENTOR Marcel A. Cordow ATTORNEY 5 Sheets-Sheet 5 Cir -4 INVENTORMarcel ,4 Cordovz D' aM/ ATTORNEY M A CORDOVI FLUORESCENT SPECTRALANALYSIS CC'W-3 I I can 4 I I cow-2 Lq, l

FIG.5

April 14, 1953 Filed Oct 24 1949 A ril 14, 1953 M. A. CORDOVI 2,635,192

' FLUORESCENT SPECTRAL ANALYSIS Filed Oct. 24, 1949 5 SheetsSheet 4PERCENT /RON PERCENT N/CKEI. 1

PERCENT CHROM/UM ANGLE 0F REFLECTION FROM ROCKSALT (2 MENTOR F I G. 6Marc?! A. Cardow Wmwu ATTORNEY April 1953 M. A. CORDOVI 2,635,192

FLUORESCENT SPECTRAL ANALYSIS Filed Oct. 24, 1949 5 Sheets-$heet 5 Q". I37 l Jfil J 37 3a BET 38 1 706 2/ 20 9 /06 FIG. 8 40 INVENTOR Mc cce/ A.Coraow' Patented Apr. 14, 1953 FLUORESCENT SPECTRAL ANALYSIS Marcel A.Cordovi, Forest Hills, N. Y., assignor, by mesne assignments, to TheBabcoek & Wilcox Company, Jersey City, N. J., a. corporation of NewJersey Application October 24, 1949, Serial No. 123,165

15 Claims.

This invention relates to the quantitative and qualitative analysis ofchemical elements and compounds, such as metals, alloys, minerals, ores,liquids, etc., with respect to their elemental constituents and, moreparticularly, to an improved crystal spectrometer for analyzing thefluorescence spectra of such elements or compounds when bombarded, forexample, by X-rays.

The theory of fluorescence analysis is based upon elementary conceptsassociated with radiation spectra. When a material is bombarded bycathode rays, the resulting X-ray emission consists of a general orcontinuous (white) spectrum and a superposed characteristic ray spectrumextending over a range of wavelengths from about to 10 centimeters. Thecontinuous spectrum is independent of the target material and itsgeneral features preclude the possibility of directly associating itWith its emission source. The monochromatic rays of the characteristicX-radiation, however, are grouped in simple series, with wavelengthsdepending upon the atomic number of the emitting element.

Emission of characteristic X-rays is due to the inner electrons of theatom. According to Bohrs theory, these electrons are supposed to occupyshells, designated as L, M, etc., around a central nucleus and to whirlaround it in the same way that the planets revolve about the sun. Thus,when an impinging electron collides with an atom of the target andejects one of its electrons, say from the innermost (K) orbit, thevacancy is filled instantly by an electron from the outer shells (L, M,etc). As a result, a line of the K series will be emitted, its energyvalue depending on the source of the replacement electron.

Wave lengths of the spectral lines comprising the K, L, M etc. seriesare inversely proportional to the square of the atomic number. In otherwords, the higher the atomic number of the target material, the shorterthe wavelength of radiation and the greater its penetrative power. The Kemission lines represent the shortest wave length group and. are themost important of the various series in view of their comparativesimplicity and high intensity. The K series of all elements, except thelightest, consists of four principal lines, of which the 111112 doubletis the most intense and closely spaced. By comparison, the L seriesspectrum is more complex in View of the numerous lines (about thirtyhave been identified) of much lesser intensity than the K series.

Chemical analysis by X-rays is made DOSSlDl-u by the specific anddistinguishing features of characteristic rays for each element in thetarget and by the direct, though not necessarily linear, relationshipexisting between the percentage of these elements and the intensities oftheir emission lines. These conditions will be satisfied also if asample is irradiated outside the X-ray tube, provided the primaryradiation is of sufliciently short wave length and the X-ray quanta haveenergies nearly approaching those of the electrons in the cathode beam.The fluorescence spectra, i. e. the line radiation resulting from theexcitation of an atom by the absorption of X-rays, can be thenconveniently identified with a crystal spectrometer. Secondaryfluorescence spectra are of much lower intensity as compared to directexcitation. This is so because, when a sample is irradiated outside theX-ray tube, the intensity of exciting radiation per unit area falls citwith the inverse square of the distance from the focal spot. Thisdrawback, however, is largely overshadowed by several importantadvantages pertaining to the secondary fluorescence spectrum which makeit the most practical source of radiation for chemical identificationpurposes.

There is now available to the art a fluorescence analyzer for use inquantitative analysis of elemental constituents in metals, minerals, andores. Some of the outstanding features claimed for this analyzer arethat (1) determinations may be made either on an absolute basis or acomparative basis on percentages up to 100%, with a reproducibility tobetter than 5%; (2) the unit does not require exceptional stabilizationof line potential; (3) determinations are independent of phase orstructure; and (4) the analyses are speedy and the unit does not requirespecialized technical training for operation.

Experimental work undertaken to evaluate this analyzer, from anindustrial viewpoint for routine chemical analyses of metallicmaterials, indicates that the above claims are not substantiated. Forexample, in out of tests, re-

producibility oi results was only between 6% and 20%, or from 1% to 15%outside the claimed accuracy range for comparative analyses, and wouldbe even further outside the claimed range if analyses were attempted onan absolute basis. In the latter case, furthermore, exceptional technical skill and tedious procedures become mandatory for evaluation ofmany correction factors such as crystal reflectivity, counter ordetector sensitivity, mutual excitation and Iinanneren unhhewn eahpleiseuhiee ten ,.ehert r e ehe h rima y rad at onem 7 absorption ofcomponent elements of the specimen, air absorption, and proportionalityfactors.

I have found further that the present commercial analyzer cannot beusefully employed for routine analyses of metals and alloys without e pto a st bil y of the l ne ne eh ie-i- In h .iree h a a se r hein l teehnelogical requirement stipulates an accuracy and reproducibility ofresults to better than 11%, and this is possible only with specialequipment assuring the highest degree of voltage stabilization.

. I have also found that, contrary to the above claims, determinationsare dependent up the structure and predominant phase of the specimen,and comparative analyses cannot be made tween samples which arechemically si.

more than one major constituent but W 11 f} structure or predominantphase. For ex nple,

a east eneeihe h eehnet e helytieei r eehiner wi h a wr ugh e 931 1 1;though eh miee l sim lar he eeinm e than the meiei'eehstitu it eel he anrt e i 0th s me and e he fi i ncies 9 the trie art ar el min t d, theinvent eh ana yzer be n e rie: eia lav ad p d to: eut ne er d iet oheheteeeei irentst l nd therth tellieinet riele- In e e te efler a be ter unrstandin f the under ng Pr n iples e he invent 1e h iet eleeeri ti n oftheee retiehei preeeeiur wi h th mentioned prior art analyzer will be oiassist:- anc This ana yze e erates the iehew s to in,

tungsten aft-ra Iiiheeeee siery 8313995128 a th s mple a e H 7,, elimatoe fii i fill to strike eerretal l zee- The etter actin s e etreetieh eretiha separates the eehie ne t e iati ns h ii] A pro e pesiio hs. refle ts hem at a the s er stic Brag a g l iv duele ente of theation are deteeted by Gag-enco nter. transmits he m ulses recei ed to anelectr ni in and cou n uhit- .(iennts a e t tehzei er a defin P ed of mea d the ercenta e of he elemen unde in est ation is h h iiby p epertio is with simi ar dat obtainedimm a samp e f known eleme tal content- A hgh o ta e ne at r is nee to ergiz the 'X- a u e. Wh eh has etilhsstetars tsealed ofi by a beryllium window. The specimen is irradiated ou ehe X-ray tub (5. le el; nd is o t si a 4.5 de rees to the axis or theeene o i eid ti -r -ye- The s mple is simila ly p t ned h e p ct to thee imator. wh c consists of a .hen y e he thi all n c tub,-

re ter; Z-ihch we nch. t-i eh e lt-iheh ons) packed into an alminumireme J of etensu ar ereseee enelhhletei ie a y 1 4 serves totransmit a nearly parallel beam of fluorescence radiation to the crystalanalyzer, which is usually rock salt or calcium fluorite.

The NaCl crystal is satisfactory for the K series of the elementsranging from about titanium (Ka1=2.74=631 A. U.) to zirconium(Ka1=0.78851 A- U 1 spectra of elements above atomic num er e dee ee ininten i in. prop to the sine of the Bragg angle. To compensate for thediminishing dispersion in the spectra of such elements, it is necessaryto use crystal planes with smaller grating constant. This requirement ispartially met by fluorite, whose atomic plane ing; (@213) plane, is 1.93A. U. as compared to a U: iet teehe plane- With this flugz escenceanalysis unit, it is possible to analyze that group of elements Whoseatomic number falls between about 22 and 50. The limited peak voltage(-50 kilovolts) in the primary X-ray spectrum is insufiicient to exciteetheiehti the eeeetree1 lement with high etemie huieh Qe t e her thewere len hs. e the li hter elemen s teete ite 'iehe htereet 9 The lemnts. ehev e hiie winter it e. anal ze b thei h e iesii ee. eihs ex endeeventing i r a s t eemee ete er the 992 .1- paratively low intensitiesof these spectra (LalIKqlZlQL '7 h The tu is elm e it eeheet meta i e no wh h t e i hi ter e tend t ese el me s eing so a an ed tet h t e 9fthe en e e y -i' rs end e i i im er nd a t heep-ee ihen- I e ter is medih e ret e ht e ih t ne eltiet ns d e'h f u e ee mehei eheei there a wh m y h ve eithewh ease/sis e e hi i n h t e t e ee eiiheh Q1. e sehderv .reele ei' e ,fie eeeeht teen. when exposed to n ihei eh ei(specimen) which is exposed to the incidentc of X-rays. The intensity ofradiati is also. fluenced by the geometrical anemggamtr the emp and etete- Oet e'tes e ofth e considerations, the specimen holderoftheanalyzer is not only impractical but also is n r to analytical errors.Its imprati'atm irg p the tedious, hence'cost yfinacljning' f spec'il.ti he t0 he ifie iiie h ie in at e et en ih'i he e e h e teki ei ee e lim e. he leees eht t h i' h ee a a er for the specimen, may be easilydeformed b he pressureexerted upon it While inserting thick specimens inthe holder. Resulting variation in the set position of the samples withrespect to the X-ray tube, will produce changes in intensity whichbecome criticalespe cially' in fthecase of elements Whichare present inresidual amounts. Another difiicultyencountered inth-e practicaloperation of the unit results during changingoi the specimens in theholder. During these 10;)- erations, the housing must be e ene' tdtiiowaccess to the specimen holder." Consequently, to prevent hazardousexposure of operatingpersonnel to X-rays, it is necessaryto'd-eeneligize the X-ray tube while the housing is openl Even thoughsuch deenergization may beof" a very small duration, such as a fewseconds for example, the restarting of the I i-ray tube takes up to tenpr more times the duration of the interruption to reach a stabilizedgondition. Thi seriouslyidelays the analytical procedure.

To overcome the foregoing defects in the specimen holder and toeliminate such delays in the analytical procedure, one feature of thepresent invention is the provision of an improved specimen holder. Thisimproved specimen holder comprises a fiat slide reciprocablelongitudinally of the external surface of an apertured wall of the X-raytube housing. The wall aperture is arranged substantially at theintersection of the X-ray cone axis with the central plane of thecollimator and has chamfered walls so as not to block any radiation. Onits inner surface, the slide has a lining of lead, and means areprovided to hold the slide firmly against such wall with the lead liningin smooth surface-to-surface jux taposition therewith.

The front or outer face of the slide has two or more longitudinallyspaced recesses in which specimens may be held by suitable clampingmeans. At substantially the center of each recess, a hole is formedthrough the slide, these holes being selectively alignable with andforming a continuation of the X-ray housing aperture by longitudinalmovement of the slide. The slide may be manually operated, butpreferably is motor driven under the control of indexing push buttons.Thereby, to align a selected specimen with the housing aperture, theoperator presses the proper push button and the motor automaticallyindexes the slide to the correct position for such specimen. Arelatively large lead shield is hingedly mounted on the housing coverand. when the apparatus is in operation, is suspended therefrom incovering relation to the portion of the slide adjacent the housingaperture.

The invention specimen holder permits a rapid succession of analyses tobe made without deactivating the X-ray tube. During movement of theholder from one indexed position to another, the housing aperture issealed by the lead lining on the inner surface of the slide, preventingexit of X-radiation from such aperture. The specimens are quickly andeasily positoned in the recesses from the front of the slide, when therecesses are out of alignment with the aperture and either side of theexternal movable lead shield or cover. For any extended break inanalysis, an externally controlled lead curtain or shield, movablymounted within the housing, may be moved to a position blocking thewindow of the X-ray tube to cooperate with the external shield inblocking exit of radiation.

As stated above, the unknown and the standard specimens being comparedmust be closely representative of each other with respect to metal.-lurgical phases, major constituents, structural conditions, and surfacepreparation. In most industrial analyses, this does not present anydiffculty, as the approximate analysis of the sample being analyzed isknown, and it is merely necessary to use a similar standard. However,with a sample whose approximate analysis is unknown, it is necessaryfirst to establish its identity qualitatively and, after the elementalconstituents have been identified, to then run a quantita tivecomparison analysis with a similar standard specimen.

A feature of the invention is the provision for making a simultaneouslyrecorded quantitative and qualitative analysis rapidly and automatically, For this purpose, a synchronous motor is used to drive thecrystal mounting arm over the goniometer scale through the area to beanalyze A synchronous motor driven recording instrument, such as arecording potentiometer, is con- 6 nected to the frequency meter circuitof the analyzer. With the recorder and the goniometer initiallysynchronized, the recorded quantitative and qualitative analysis can becarried out without manual attention.

The analysis is depicted by a graph line on the recorder chart. Provideda properly calibrated chart is utilized, the quantitative analysis canbe made on an absolute basis, 1. e. without the use of a standardspecimen for comparison analyses. This requires a difierently calibratedchart for the different types of alloys or compositions being analyzed.For example, the calibration of the percentage scale for chromium instraight chromium (ferritic) steels would diiier from the calibration ofthe percentage scale for chromium in chromium-nickel (austenitic)steels. The calibrated charts may take any one of several forms. Ifquantitative analyses are being made solely for chromium, charts may beused which have a plurality of chromium percentage scales eachcalibrated for the chromium percentages in different types of chromiumbearing alloys. On the other hand, if quantitative and qualitativeanalyses are being made for all the elemental constituents of selectedspecimens, the charts used will have calibrated percentage scales forall elements, such as iron, nickel, chromium, etc., of a particular typeof alloy, charts having differently calibrated percentage scales beingused for each different type of alloy. To determine the particular typeof alloy to which an unknown specimen is germane, a rapid, qualitativeand relatively quantitative analysis can be made before the finalquantitative analysis.

The elemental analysis to classify an unknown specimen may be greatlyfacilitated by the use of standard charts for comparison with therecorded chart produced by the elemental analysis. For example, withstandard charts prepared for 18-8, 25-20, and other alloys, a comparisonof the standard charts with the recorded chart will provide anindication of the relative chart peaks and their relative locations.Thus, the magnitudes of the similarly located peaks may be com-- paredto obtain an approximation of the relative intensities of radiation,thereby classifying the specimen as to type.

To facilitate these analyses, a push button control of the scanningoperation is provided. Additionally, the specimen holder may be motoroperated between its analyzing positions under the control of pushbuttons and limit switches.

Experimental analyses have further shown that an analyzer arrangementinvolving angles of 45 between the sample and the axis of the incidentcone of X-ray and between the collimator and the sample, thus providingan included angle of between the X-ray cone axis and the collimator, isnot always the best angular arrangement for optimum results. Forinstance, incident angles, other than 45, in the range from 30 to 60produce better results with certain elements. Accordingly, the inventionanalyzer is capable of adjustment of the angular relationships.

For accurate reproducibility of results, it is essential to constantlymaintain a uniform atmosphere for the passage of the radiation from thespecimen through the collimator and past the analyzer to the radiationdetector. The aforementioned air absorption may be reduced by using aninert gas, such as helium, for the uniform a"- mosphere, or the systemmay be evacuated. For this purpose, the invention analyzer includes agas-tight housing for the X-ray tube, into which the collimator extendsin sealed relation, and a flexible gas-tight hood interconnecting theradiation detector and the outer endof the collimator and enclosing. thecrystal analyzer. The enclosed system may be connected to a suitablesource of an inert gas or may be connected to a vacuum pump, as may benecessary or desirable during a particular analysis.

In ananalyzer adapted for routine production analysesof metallicmaterials, the. protection and mounting of the crystal analyzer areimportant in securing uniform results and in facilitating the analyses.To prevent any change in the, reflectivity properties of the crystalanalyzer, such as due tov hygroscopic action, the crystal analyzer iscoated with an extremely thin coating of. a pro.- tective material, suchas liquid envelope. r example, which Weatherproofs the surface of thecrystal analyzer without aife'cting the characteristics of the crystalanalyzer. Also, in setting up the apparatus, the crystal analyzer mustbe carefully adjusted both angularly and otherwise, to obtain theoptimum reflecting relation to. the radiation detector. This initialadjustmentmust be carefully made. and requires, a considerable amount oftime. If the crystal analyzer is replaced, the time consuming initialadjustment must be performed again. To; eliminate this undesirablere-adjustment, the crystal holder of the invention analyzer is. providedwith micrometer adjustments, whereby a record of the optimum settingsfor difierent crystals may be made and such settings rapidly reproduced.

With the foregoing in mind, it is an object of the invention to providean improved X-ray type crystal spectrometer or analyzer for analysis ofcompositions utilizing fluorescent radiation therefrom and which isparticularly eficient in the accurate analyses of metals and alloys.

Another object is to provide such an analyzer having an improvedspecimen holder capable of providing more accurate and speedieranalytical results.

A further object is to provide such an analyzer in which a suitable gasor evacuation is employed as a means of providing a uniform atmosphere,other than air, thereby eliminating absorption of radiation.

Yet another object is to provide such an analyzer including automaticspecimen holder positioning means and automatic scanning means.

Still a further object is to provide such an analyzer including meansfor making direct quantitative analyses of the elemental constituents ofunknown compositions of known types.

An additional object is to provide such an analyzer in which. it is notnecessary to interrupt the X-ray tube energization between analyses.

Another and additional object is to provide a fluorescence spectraanalyzer with which a quantitative analysis of an unknown specimen maybe made by simultaneously analyzing the unknown specimen and acomparison or standard specimen of the same type as the unknown andcharting the differential intensities of radiation at commoncharacteristic Bragg angles.

These and other objects, advantages and novel features of the inventionwill be apparent from the following description and the accompanyingdrawings. In the drawings:

Fig. 1 is a plan view of a fluorescence analyzer in accordance with thepresent invention, the drive for the specimen holder being omitted tosimplify the illustration;

8 Fig. 2 is an elevation view of the analyzer, showing improved specimenholder and its drive;

Fig. 3 is an end elevation view of the specimen holder and a portion ofthe X-ray tube housing;

Fig. 4 is. a schematic wiring diagram of the tively analyze a known andan unknown speci men, and record the difierential intensities ofradiations at common characteristic Bra angles;

Fig. 8 is a partial schematic plan view, corresponding to Fig. 7, butusing a single X-raytube; and

Fig. 9 is a partial schematic elevation viewof the X-ray tube andspecimen of Fig. 8.

Referring more par icularlyto' Figs. 1-, 2,- and 3 of the drawings, theanalyzer ill includes a base plate i, of aluminum, steel, or anydesired: material, on which is mounted a housing id, of suitable metal,having a removable cover It. In plan, housing 5 and its cover l2 may,for examplabe triangles, with the vertex angle being opposite the longerforward wall is which extends beyond the other walls M, it of thehousing at either end. The interior of housing is is lead lined, asindicated at H, and cover 12 has lead-lining it on its under surface.

Within housing t5, adjacent wall it and substantially midway of thelatter, is mounted an X-ray tube having water cooling connections asindicated at 25, 22. The axis of the X=ray cone, inv the angularrelations shown in Fig. 1-, is directed at 45 to wall it and intersects.the collimator cone axis substantially at the outer surface of wall isand at the center of aperture 25. Collimator comprises a honeycomb ofthin walled nickel tubing packed into an elongated, rectangular aluminumframe. Alternatively, the frame may be transversely subdivided byclosely spaced, parallel longitudinal partitions to form a plurality ofelongated slits extending through the frame. Within housing i5,collimator 30 carries a pair of brackets 2 3, 24 which slidably supporta rod 26 extending through wall l land having an operating handle 2'! onits outer end. On its inner end, rod 26 supports a lead shield orcurtain 28 for longitudinal movement into and out of a positionintercepting X-rays directed from tube 29 toward aperture 25 andessentially blocking the X-ray tube Window.

It has been found that maximum excitation of the characteristic spectraof certain elements is obtained when the element is bombarded by aprimary X-ray beam at angles smaller or larger than but usually lyingbetween 80 and For this reason, tube 25 is mounted for adjustment alongan arcuate track is having its center at the intersection of the X-raycone axis and the collimator axis.

The X-rays from tube 28 directed through aperture 25 impinge, at theselected angle, upon a specimen mounted. in a manner to be described, inflush relation with the outer surface of wall 3. The resultant secondaryfluorescent spectra from the irradiated specimen are directed throughthe" collimator 5G and allowed to strike acrystal analyzer 35. Thelatter acts, as previously stated,

as' a diffraction grating to separate the component spectra and, byproper positioning, to reflect them at a characteristic Bragg angle. Theindividual quanta of radiation are detected by a Geiger counter 40 whichtransmits the received impulses to an electronic scaling and countingunit 45 (Fig. 6).

For this purpose, and in accordance with the present invention, crystalanalyzer 35 and Geiger counter 40 are mounted on a -90 goniometer 58having one fixed radial arm 3! aligned with collimator 30 and anotherfixed radial arm 32 perpendicular thereto, the outer ends of the fixedarms being interconnected by a quadrant 33 having arcuate racks 34 and33 along its radially inner and outer edges, respectively, and beinggraduated from 0 to 90. Crystal analyzer 35 is mounted on the inner endof a movable radial arm 31 pivoted at the axis of goniometer 53, andGeiger counter 40 is mounted on another movable radial arm 38 likewisepivoted at the goniometer axis.

In the operation of the apparatus so far described, arms 31 and 38 areangularly adjusted along quadrant 33 to change the angle of crystalanalyzer 35 relative to collimator 3B and the angle of Geiger counter asrelative to analyzer 35. During such adjustment, the angle between arm3! and arm 3| is substantially one-half the angle between arm 38 and arm3i, with a tolerance of several degrees of the secondary arm 31. Inother words the angle between the axes of Geiger counter 40 andcollimator 3a is always substantially twice the angle between the planeof crystal analyzer 35 and the collimator axis. The characteristic Braggangle for any particular element is the angle between arms 31 and 38when the spectra due to such elements are at a maximum intensity asindicated by Geiger counter at and counting and scaling unit 45. Theforegoing angular relations of the collimator, crystal analyzer, andGeiger counter are known to the art.

In known fluorescent analyzers, arms 3?, 38 are manually adjusted overquadrant 33, a Vernier adjustment being provided on one or both arms. Inthe present invention, and as somewhat schematically indicated in Fig.l, a small reversible motor 4! is mounted on a bracket 42 on arms 3'!and includes a worm drive l3 arranged to drive a pinion 44 meshing withthe outer rac 3c of quadrant 33. Similarly, a small reversible motor 45on a bracket 41 on arm 38 has a worm reduction unit 48 driving a pinion49 meshing with inner rack 3-1 of quadrant 33. To provide the describedangular relation of arms 3! and 38, motor 4|, and its drive 43, 44, isarranged to operate arm 3! at substantially one-half the rate ofoperation of arm 38 by motor 46 and its drive 48, 49. The describeddriving arrangements form part of an automatic scanning system whichwill be described more fully in connection with the schematic wiringdiagram of Fig. 5.

In order to assure accurate reproducibility of results, it is absolutelyessential that a uniform atmosphere be constantly maintained between theirradiated specimen and the radiation detector. If an inert gas, such ashelium, is introduced into the system, the air absorption of radiationsmay be reduced. Furthermore, evacuation of the system will eliminateradiation absorption by air. In either case, the system must be sealedbetween the specimen and the entrance to the Geiger counter.

The housing Hi can be made substantially air tight due to thecompressibility of the lead linings ll, [8, or a sealing gasket can beused between the housing and its cover, and collimator 30 and rod 26 canbe mounted in air tight relation through the wall I4, aperture 25 beingsealed by the specimen holder and specimens, as will be described. Aflexible, gas-tight sleeve 55, of rubber or similar material,interconnects the outer end of collimator 30 to the inner end of Geigercounter t0, being sealed to both of these elements and enclosing crystalanalyzer 35. A connection 5| is provided on sleeve 55 and may beconnected to a suitable source of an inert gas, or to a vacuum pump,dependent upon the desired conditions. Such connection may, of course,be located elsewherein the system, as at the housing I5.

It should be noted, at this point, that aperture 25 is suitablychamfered or bevelled so that there is substantially no obstruction tothe X-rays entering the aperture and, more importantly, to thefluorescent spectra passing from the specimen to the collimator 30.Also, the illustrated arrangement of X-ray tube 29 and collimator 38substantially decreases the distance between the tube and the specimen,as compared to prior arrangements in which the specimens were mounted inan indexing holder within the housing I5. For example, the X-ray tube is/8" closer the specimen than hitherto possible. As the intensity ofsecondary radiation is inversely proportional to the square of thedistance between the X-ray tube and the sample, any decrease in suchdistance is very markedly effective in increasin the inten sities of thefluorescent spectra.

Another improvement is in the collimator; In known prior art analyzers,the collimator is packed with fa" diameter nickel tubing. By packing thecollimator with s 2 nickel tubing, or by providing it with closelyspaced, slit-forming separators of suitable thickness, the resolution ofthe spectra is greatly improved but at a small sacrifice in intensity.However, such reduction in intensity is more than compensated by theabovementioned decrease in the distance between the X-ray tube 20 andthe specimen.

To weatherproof crystal analyzer 35, when the latter is hygroscopic, forexample, the crystal analyzer is provided with a very thin film of acoating, such as the one known to the art as liquid envelope. Thiscoating when properly applied, does not interfere with the diffractiongrating action of the crystal analyzer.

The construction and mounting of the novel specimen holder 6|] will bebest understood by reference to Figs. 1, 2, and 3. The upper section ofwall l3 of housing I5 is reduced in thickness, by machining or the like,providing a shoulder 52. On the thicker wall portion below this shoulderare mounted a pair of rails 33, extending longitudinally of wall i3 andin vertically spaced relation to each other. Rails 53 are secured bybolts 54 to wall l3, and each rail has a longitudinally extending,semi-cylindrical groove 56 in one horizontal surface, the groovesopening in opposed vertical directions as seen in Fig. 3.

Specimen holder .60 includes a vertical panel 6| substantially alignedwith shoulder 52. The rear surface of panel 6| has a longitudinalchannel 62 therein containing a lead lining 63, channel 62 and itslining being aligned with aperture 25 and extending a substantial amountabove and below the same. The forward face of panel 6i is formed with apair of longitudinally spaced, vertically extending grooves 64, 64, thebase of each having a chamfered hole 65, 65 each somewhat larger thanaperture 25. When the correspondin groove is longitudinally centeredwith aperture 25 its hole 65 or B is aligned with the aperture. Holes55, 65' extend through lead lining $3.

Grooves 6t, 5t receive the specimens l9, it, respectively, one of whichmay be an unknown and the other a standard, or vice versa. To hold thespecimens against the bases of the grooves, bolts or studs 6%, 66 extendoutwardly on each side of each groove. Each pair of bolts supports a barEl, 6? having a stud as, $8 centrally mounted therethrough and formedwith a hardened point H, i l to engage a specimen. Nuts l2, 12 mountedon studs 55, 6t compress springs 59, 69 engaging bars 6'5, ti. When inposition, specimens l e, lil rest on blocks l3. l3, respectively, set inthe lower ends of grooves 6 3, st, and are held flush against the basesof the recesses by the pointed studs 63, $8.

Specimen holder 63 is supported for longitudinalsliding movement ontracks 53, 53 in the following manner. An elongated bar '53 has, in itsupper surface, a semi-cylindrical groove i i complementing groove 56 oflower track 53, and groove 14 has secured therein plugs 76 retainingball bearings engaged in groove A block ll has, in its'flo'wer surface,a semi-cylindrical groove is complementary to' groove 56 of upper track53 and having secured therein plugs Si retaining ball bearings in uppergroove 55. Bar l3 and block ll have vertical inner surfaces engaged withwall I 3. The outermost surface 82 of block I! is tapered for.cooperation with the tapered surface of a horizontally elongated wedge33. Block El and wedge 33 cooperatively form a T-slot receiving aninverted T-bar 8 A vertical cover plate 85 is secured to the outersurfaces of bar 73 and wedge 83.

The vertical panel 3! is secured to a rectangular bar 8? which isadjustably secured to the stem of T-bar 84 by studs 88. As these studsare tightened, T-bar 84 is drawn toward bar 8?, but its upward movementis limited by the portion of the T-slot formed in block ii. A force isexerted downwardly on wedge 83 by bar 8?, in turn forcins T-bar 8t andbar 8'! inwardly toward wall is. Thisacts to force panel st, andparticularly lead lining 63, tightly against the surface of wall 13. Toprotect against the X-rays passing through specimens 18,75, a leadshield it, of substantial extent, is hingedly mounted on cover 12 inalignment with aperture 25 so that it covers whichever specimen isaligned with the aperture.

Specimen holder to may be manually operated to selectively positionspecimens 7 8, to in front of aperture 25 for irradiation by X-ray tube28. Preferably, however, the specimen holder is automaticallyselectively positioned under control of push buttons 8 and? (Fig. l)which may be conveniently mounted on plate I i. For this purpose, a nut88 is secured to the inner surface of plate 86 and has a cylindricalbore receiving a reversely threaded screw 98 engaged by a pin 9! in' thebore of nut 80. As shaft 90 is continuously rotated in one direction,pin 93 travels alternately along each of the reversely directed threadsto reciprocate holder til. Shaft 99 is rotated by a motor 95 through themedium of reduction gearing 9i serving to mount'one end of the shaft.The opposite shaft end is rotatably supported in a bearing bracket 92 onplate H.

The operation of the automatic holder positioning'system will be clearfrom Figs. 3 and 4. A limit switch operator 93 is secured to plate 86and; is arranged to open either or a pair of nor,-

i2 mally closed limit switches 94, 98, one at each limit of travel ofholder 60 and both connected in series with motor 95. Switches 94, 96are so located as to open the circuit of motor -whenever one or theother of the specimens 7!}, 70' is" analysis position, operator 93vengages and opens switch 965 to stop movement of holder 60., Poshtioning of specimen it in the analysis position is. effected by pressingpush button I shunting:

switch 536. Holder 59 may be stopped in any intermediate position byoperating push button Bl which, while shown as a push button, may be anon-off snap switch.

The automatic positioning control arrange:-

ment of Fig. 4 is used in making analyses wherein an unknown specimenlei is compared with a known specimen iii having an analysis and PTO.duction history comparable to that of the un:

known specimen. Holder 5! is positioned at an.

intermediate location with lead lining 63 efiece tively sealing aperture25 so that the X-ray tube may be activated to warm-up while theknown andunknown specimens are being clamped in holder 68. Rod 25 is preferablymoved inward to position shield 28 in front of the X-raytubewindow toblock X-rays from aperture 25.v The specimens are preferably preparedwitha flat ground surface finished with emery paper. After the specimenshave been positioned, shield 28 is withdrawn, lead shield l5 is loweredover the holder, switch 97 is closed, and push button I operated toposition specimen It in front of aperture 25.

Specimen it is then analyzed by shifting arms 37, 38 over the quadrant33, the counts from Geiger counter to being totaled over a mode:termined time interval at each characteristic Bragg angle position. Thisoperation may be effected manually or specimen iii may be auto.-matically scanned, as will be described in con-.-

nection with Fig. 5. When analysis of specimen 753 is completed, pushbutton 2 is operated to position unknown specimen it in front ofaperture 25, and specimen iii is analyzed in the same manner. Comparisonof the two analyses will provide a quantitative analysis of specimen 70'within the accepted limits of accuracy and re-. producibility ofresults. To insure such accuracy, a sensitive voltage stabilizer isincluded in the energizing circuit X-ray tube 29, asfthere' isadirectrelation between intensity of fluorescence and the voltage across theX-ray tube. With the usual line potential fluctuations common in industrial plants, such X-ray tube voltage stabilization is of the utmostimportance for accurate analyses.

Fig. 5 schematically illustrates an automatic scanning arrangementutilizing the motors El and .6 driving arms 37 and 38, respectively,through the associated reduction gearings 433 and 48. As stated, arm 38is moved at substantially twice the speed of arm 31 so that the anglebe-.- tween arms 3| and 38 is substantially twice that between arms 3!and 31. The counting and scaling unit 45, having its input connected toGeiger counter 40, has its output applied to a recording potentiometerHit. The chart ID! of the potentiometer is driven by a motor H32,preferably synchronous, in such manner that, with the chart calibratedin Bragg angle degrees, its calibrations will be synchronized with thecharacteristic Bragg angl s as read from goniometer 50. As arms 33, 33move over quadrant 33, chart I! is correspondingly moved so that themovable needle or pen (not shown) of recorder M10 is always at a pointon the chart corresponding to the Bragg angle determined from goniometerB. The pen is moved in accordance with the intensity of fluorescentradiation, as registered by Geiger counter 4t and translated by unit 45for application to recorder Hi8. Consequently, a graphic qualitativeanalysis of a specimen is quickly produced on chart 101 by the automaticscanning arangement.

If chart H3] is suitably calibrated to indicate percentages of elementalconstituents, a rapid quantitative analysis may also be produced by theautomatic scanning arrangement. Such quantitative analyses requireindividual charts for each type of composition, such as for a lowstraight chromium alloy, a chrome-nickel austenitic alloy, etc.Additionally, the charts have independent percentage scales for eachlemental constituent, such as a chromium scale, copper scale, ironscale, etc., dependent upon the type of alloy undergoing analysis. Foranalyzing quantitatively for a single element in an unknown specimen,charts may be used havin differently calibrated percentage scales forsuch element, each scale corresponding to a particular type of alloy, orthe like. These charts are prepared empirically by fluorescent analysisof specimens of known percentage compositions, and their use obviatesthe necessity for comparative analyses utilizing standard specimens ofknown composition.

Referring to Fig. 5, a supply circuit is indicated as includingconductors 563, Hi l. Operation of arms 3i, 38 in a clockwise directionis effected by a relay CW which is energized by operation of push button3. Closure of contacts CW-l completes a holding circuit for the relaythrough closed contacts CCW-E of counterclockwise relay CCW, clockwiselimit switch LS-i, and stop push button 5. Contacts CW-3 and CW- l closeto energize all three motors 4!, it, and N32 for operation of th systemin the clockwise scanning direction. The scanning may be continued untillimit switch LS-l opens, or may be limited to a particular area ofinterest by operating stop push button 5.

counterclockwise scanning is effected in a similar manner by energizingcounterclockwise relay CCW through momentary depression of push button4. It will be noted that contacts CW-2 and CCW-2 interlock the relaycircuits so that only one circuit can be closed at a time. While threemotors are shown for the system, if greater assurance of synchronism ofthe chart movement with the goniometer movement is desired, chart it!can be driven by motor 4! or motor fit. Thereby, the chart operation ismechanically locked to the goniometer operation.

The automatic scanning system provides for rapid qualitative and/orquantitative analyses without the time consuming mathematicalcomputations necessary with manual scanning, thus greatly expediting theanalytical procedure.

.An outstanding feature of the apparatus is that the size of thespecimens is not limited by the size of grooves 64, 64. Should it bedesired to analyze a specimen which is too large to fit in one of thesegrooves, holder 66 can be readily removed by loosening studs 88 anddetaching bar 2'! from T-bar 84. With bar 8? and panel 6| removed, theoutsize specimen can be clamped to wall [3 directly in front of aperture25. Should either specimen be smaller than an opening E5, 65', a sleeveor a shim of appropriate size may be inserted in the opening.

Fig. 6 is a reproduction of actual graphic analyses of two structurallysimilar alloys of the same predominant phase, both analyses beingrecorded on the same chart. The solid line A is the recorded analysis ofan alloy of 18.25% chrome, 8.78% nickel, balance substantially iron,while the broken line B is th recorded analysis of an alloy of 25.14%chrome, 20.28% nickel, balance substantially iron. The respective curveswere recorded on a quadrilaterally ruled chart having calibratedpercentage scales for chromium, nickel and iron, the abscissaecorresponding to characteristic Bragg angles.

By reference to the chart, it will be noted that the Ni K0. point of thebroken line B, representing 20.28% Ni is a little over twice themagnitude of the corresponding point of the solid line A representing8.78% Ni. Similarly, the Cr Kc peak of the broken line B, representing25.14% C1 is about higher than the corresponding peak of solid line A,representing 18.25% Cr. The two Fe Kc peaks are likewise proportional tothe respective Fe percentages.

The depicted chart has calibrated percentage scales for nickel, iron andchromium in austenitic alloys of the chromium-nickel type. For othertypes of alloys, differently calibrated percentage scales are used.Alternatively, the chart may have only chromium scales, for example,each calibrated for the chromium percentage in a different type ofalloy. fhe latter type of calibrated chart is particularly useful inanalyzing for a single constituent such as chromium, nickel, etc.Additionally, the charts are calibrated in accordance with theparticular crystal analyzer used, such as rock salt, fluorite, etc.

Figs. '7, S and 9 schematically illustrate the invention analyzer asarranged for making comparative analyses by simultaneously irradiatingboth the standard and unknown specimens from a single source of primaryradiation and recording the differentials of the percentages of theconstituents to quantitatively analyze the unknown specimen. In thesefigures, the apparatus elements have been given the same referencenumerals, primed or double-primed when duplicated, as used in Figs. 1through 5.

In the arrangement of Fig. 7, the known specimen Hi and the unknownspecimen it, both mounted in specimen holders (not shown) on outer wallsurfaces of housing It are simultaneously irradiated by a single sourceof primary radiation, such as an X-ray tube 26 having two windows 23 and23". The resulting characteristic secondary radiation from specimen 1Bis rectified by collimator 3U, diffracted by crystal analyzer 35, andthe component spectra at selected Bragg angles detected by a Geigercounter 453.;

The latter, and analyzer 35, are mounted on arms 38, 3'1, respectively,movable over quadrant 33 by synchronized motors, as previouslydescribed. The characteristic secondary radiation of specimen lli isrectified by collimator 30', diffracted and detected in the same manner,the corre-- i spending elements bearing the same reference charactersprimed.

The output of detector iii is applied, through leads iilS to a scalingand counting unit energized from source till. Similarly, the output ofdetector id is applied through leads it? to scaling and counting unitd5" lizewise energized from source it]. The outputs of units i5, it areapplied, through leads 1'58, i 58, respectively, and in opposition, tothe grid ii i of anelectronic valve Hi The latter has an anode M2connected to 33+ through a recording potentiometer lee" energized fromsource it and having its chart movement coordinated with the movementsof the goniometer arms, as described in connection with Fig. 5. Cathodeiii of valve lid is schematically indicated :as grounded, with the gridbias being derived by an adjustabl resistancei-id.

In operation, the goniometers 5d, 5d are adi justed to knowncorresponding points where the outputs .of units 55, it are balanced,and resistance lid adjusted until the recorder movable element is on thezero percentage difference line of the recorder chart. The two specimensto, it are then simultaneously irradiated, and scanned in the mannerdescribed for Fig. 5. The differences between the outputs of units t5,i5 is recorded, on a properly calibrated recorder chart, as percentagedifierentials at characteristic Bragg angles with the quantitativeanalysis of specimen 79 being known, that of specimen iii" is readilycomputed :from the graphic representation on the chart.

:Figs. 8 and.9 illustrate an alternative arrangement for simultaneouslyirradiating both specimens from a single source, such as X-ray tube 2%having a single window '23. The specimens iii, fiilflare arranged oneabove the other, in front of but at substantially different angles towindow 23, a 90 relation being shown by way of example. A horizontal.lead shield ii'5 keeps the characteristic secondary radiation beamsseparated for rectification by appropriately directed collimators '39and 36'. The remainder of the arrangement, and its operation, areidentical to those of Fig. '7.

While anX-ray tube has been referred to as the source ofprimaryradiation, this has been by way of example only. To obtain theprimary radiation incident upon the specimen, radiation sources .cotherthan an X-ray tube may be used, such as, for example, radium or asuitable isotope of a radio-active material.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the inventionprinciples, it will beunderstood that the invention may be embodiedotherwise without departing from such principles.

I claim:

1. In a-fluorescent spectra analyzer of .the type comprising a radiationsource for directing primary radiation onto aspecimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimator inthe pathof thecharacteristic secondary radiation and-operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiationirom the grating, means mounting thegrating detector for angular adjustment relative to each other and tothe incident secondary radiation for detecting the component spectra atselected Bragg angles; a lead lined housing enclosing the radiationsource and the entrance end of the collimator and having a side wall,said wall having an aperture therethrough and the radiation source andcollimator being so arranged that the axes of the primary and secondaryradiation beams intersect substantially adjacent the outer surface-ofsaid Walland at the center of the aperture; a panel movably mounted onthe outersurface of said wall, in 'suriace to-surface engagementtherewith, and having a lead lining on its well engaging surface of anarea greater than that of the aperture; said panel having an openingtherethrough alignable with the wall aperture; and means operable toposition a specimen on the outer side of said panel and overlying theopening therein; said panel being movable on said wall between aposition in which its lead lining covers the wall aperture and aposition in which the opening is aligned with the aperture.

2. Ina fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimater in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiaticn from the grating, means mounting thegrating and detector for angular adjustment relative to each other andto the incident secondary 'radiation for detecting the component spectraat selected Bragg angles; a lead lined housing en-' closing thegenerator and the entrance end of the collimator and having a side wall,said housing being substantially airtight and said collimator extendingin sealed relation through a wall thereof a flexible air-tight enclosureconnecting the outer end of the collimator to the detector and enclosingthe diffraction grating and means operable to constantly maintain auniform atmosphere other than air in said :housing, collimator, andenclosure to minimize or eliminate absorption of fluorescent spectrabetween the specimen and the detector.

3. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate thesameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, means mountingthegrating and detector for angular adjustment relative to each otherand to the incident secondary radiation for detecting the componentspectra at selected Bragg angles; a lead lined housing onclosing theradiation source and the entrance end of the-collim tor and having aside wall, said wall having an aperture therethrough and theradiationsource and collimatorbeing so arranged that the axes of theprimary and secondary radiation beams intersect substantially adjacentthe outer surface of said wall and-at the center of the aperture; anelongated panel mounted in surface-to-surface engagement with the outersurface of said wall and 'reciprocable longitudinally thereof, andhaving a lead lining on its wall engaging surface of an area greaterthan that of the aperture; said panel having longitudinally spacedopenings therein selectively alignable with the wall aperture; and meansoperable to position specimens on the outer side of said panel and eachoverlying an opening therein; said panel being movable on said wallbetween posit ns in wh its lead lining covers the wall aperture andpositions in which the openings are selectively aligned with theaperture.

4. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction grattingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, means mounting thegrating and detector for angular adjustment relative to each other andto the incident secondary radiation for detecting the component spectraat selected Bragg angles; a lead lined housing enclosing the radiationsource and the entrance end of the collimator and having a side wall,said Wall having an aperture therethrough and the radiation source andcollimator being so arranged that the axes of the primary and secondaryradiation beams intersect substantially adjacent the outer surface ofsaid wall and at the center of the aperture; an elongated panel mountedin surface-to-surface engagement with the outer surface of said wall andreciprocable longitudinally thereof, and having a lead lining on itswall engaging surface of an area greater than that of the aperture; saidpanel having longitudinally spaced openings therein selectivelyalignable with the wall aperture; means operable to position specimenson the outer side of said panel and each overlying an opening therein;mechanism, including an electric motor, operable to reciprocate saidpanel along said wall; control means operable to energize said motor;and means automatically operable to deenergize said motor whenever anopening is aligned with the aperture; the lead lining of said panelsealing the aperture in intermediate positions of said panel.

5. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, means mounting thegrating and detector for angular adjustment relative to each other andto the incident secondary radiation for detecting the component spectraat selected Bragg angles; a lead lined housing enclosing the radiationsource and the entrance end of the collimator and having a side wall,said wall having an aperture therethrough and the radiation source ndcollimator being so arranged that the axes of the primary and secondaryradiation beams intersect substantially adjacent the outer surface ofsaid wall and at the center of the aperture; a slide mounted forlongitudinal reciprocation on the outer surface of said wall; anelongated panel disengageably supported on said slide in surface-tosurface engagement with the outer surface of said wall, and having alead lining on its wall engaging surface of an area greater than that ofthe aperture; said panel having longitudinally spaced openings thereinselectively alignable with the wall aperture; and means operable toposition specimens on the outer side of said panel and each overlying anopening therein; said slide being movable between positions in which thelead lining of said panel covers the aperture and positions in which apanel opening is selectively aligned with the aperture.

6. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, means mounting thegrating and detector for angular adjustment relative to each other andto the incident secondary radiation for detecting the component spectraat selected Bragg angles; a lead lined housing enclosing the radiationsource and the entrance end of the collimator and having a side wall,said wall having an aperture therethrough and the radiation source andcollimator being so arranged that the axes of the primary and secondaryradiation beams intersect substantially adjacent the outer surface ofsaid wall and at the center of the aperture; a slide mounted forlongitudinal reciprocation on the outer surface of said wall; anelongated panel disengageably supported on said slide insurface-to-surface engagement with the outer surface of said wall, andhaving a lead lining on its Wall engaging sur-- face of an area greaterthan that of the aperture; said panel having longitudinally spacedopenings therein selectively alignable with the wall aperture; meansoperable to position specimens on the outer side of said panel and eachoverlying an opening therein; and wedge means cooperable with said slideto force said panel into tight surface engagement with the outer surfaceof said wall; said slide being movable between positions in which thelead lining of said panel covers the aperture and positions in which apanel opening is selectively aligned with the aperture.

'7. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, means mounting thegrating and detector for angular adjustment relative to each other andto the incident secondary radiation for detecting the component spectraat selected Bragg angles; a lead lined 11. In a fluorescent spectraanalyzer of the type comprising a radiation source for directing primaryradiation onto a specimen to irradiate the same, a collimator forresolving the resulting characteristic secondary radiation emanatingfrom the irradiated specimen, a diffraction grating arranged adjacentthe exit end of the collimator in the path of the characteristicsecondary radiation and operative to separate the same into itscomponent spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, and means mountingthe grating and detector for angular adjustment relative to each otherand to the incident secondary radiation for detecting the componentspectra at selected Bragg angles, the mounting means comprising a pairof radial arms relatively adjustable about a center adjacent the exitend of the collimator, one of said arms supporting said grating forangular adjustment relative to the axis of said collimator and the otherarm supporting said detector for angular adjustment relative to saidgrating and the axis of said collimator; an automatic specimen scanningsystem including a movable chart recorder having its chart calibrated inBragg angles; means operative to apply the output of said detector tothe indicating mechanism of said recorder; and driving means associatedwith each of said arms and with said chart and operable to drive saidarms '9 and said chart in coordinated relation with each other toproduce a record of the relative intensities of secondary radiation atcharacteristic Bragg angles.

12. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, and means mountingthe grating and detector for angular adjustment relative to each otherand to the incident secondary radiation for detecting the componentspectra at selected Bragg angles, the mounting means comprising a pairof radial arms relatively adjustable about a center adjacent the exitend of the collimator, one of said arms supporting said grating forangular adjustment relative to the axis of said collimator and the otherarm supporting said detector for angular adjustment relative to saidgrating and the axis of said collimator; an automatic specimen scanningsystem including a movable chart recorder having its chart calibrated inBragg angles; means operative to apply the output of said detector tothe indicating mechanism of said recorder; driving means associated witheach of said arms and with said chart and operable to drive said armsand said chart in coordinated relation with each other to produce arecord of the relative intensities of secondary radiation atcharacteristic Bragg angles; and a conjoint control system for saidmotors including manually operable circuit closure means, automaticcircuit breaker means operative at the limits of movement of the arms,and manually operable circuit breaker means.

13. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a difiraction gratingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, means mounting thegrating and detector for angular adjustment relative to each other andto the incident secondary radiation for detecting the component spectraat selected Bragg angles; a lead lined housing enclosing the generatorand the entrance end of the collimator and having a side wall, saidhousing being substantially air-tight and said collimator extending insealed relation through a wall thereof; a flexible air-tight enclosureconnecting the outer end of the collimator to the detector and enclosingthe diffraction grating; and means operable to constantly maintain avacuum in said housing, collimator, and enclosure to minimize oreliminate absorption of fluorescent spectra between the specimen and thedetector.

14. In a fluorescent spectra analyzer of the type comprising a radiationsource for directing primary radiation onto a specimen to irradiate thesame, a collimator for resolving the resulting characteristic secondaryradiation emanating from the irradiated specimen, a diffraction gratingarranged adjacent the exit end of the collimator in the path of thecharacteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receivecharacteristic secondary radiation from the grating, means mounting thegrating and detector for angular adjustment reltative to each other andto the incident secondary radiation for detecting the component spectraat selected Bragg angles; a recorder chart calibrated in characteristicBragg angles and having percentage scales for elemental constituentscalibrated in accordance with known relations of spectral intensities toelement percentages; and means constructed and arranged to indicate onsaid chart at each characteristic Bragg angle the spectral intensity;whereby an unknown specimen may be simultaneously quantitatively andqualitatively analyzed.

15. For use in a fluorescent spectra analyzer of the type comprising aradiation source for directing primary radiation onto a specimen toirradiate the same, a collimator for resolving the resultingcharacteristic secondary radiation emanating from the irradiatedspecimen, a diffraction grating arranged adjacent the exit end of thecollimator in the path of the characteristic secondary radiation andoperative to separate the same into its component spectra, a radiationdetector arranged to receive characteristic secondary radiation from thegrating, means mounting the grating and detector for angular adjustmentrelative to each other and to the incident secondary radiation fordetecting the component spectra at selected Bragg angles, the mountingmeans comprising a pair of radial arms relatively adjustable about acenter adjacent the exit end of the collimator, one of said armssupporting said grating for angular adjustment relative to the axis ofsaid collimator and the other arm supporting said detector for angularadjustment relative to said grating and the axis of said collimator, anautomatic specimen scanning system including a movable chart 2?;recorder, means operative to apply the output of said detector to theindicating mechanism of said recorder, driving means associated witheach of said arms and with said recorder and operable to drive said armsand said recorder in coordinated relation with each other to produce arecord of the relative intensities of secondary radiation atcharacteristic Bragg angles; a chart for said recorder calibrated incharacteristic Bragg angles and having percentage scales for elementconstituentscalibrated in accordance with known relations of spectralintensities to element percentages, to quantitatively determinethe-composition of the test specimen.

MARCEL A; CORDOVI.

References Cited in the file Of this patent UNITED STATES PATENTS NumberOTHER, REFERENCES A new Precision X-Ray Spectrometer by W 13 15 terSoller, Physical Review, vol. 24, 1924, pp.

A High-Temperature X-Ray Camera for Precision Measurements, Jay,Physical Society of London Proceedings, vol. 44; 1933, pages 635-642.

